Sprocket 20B-3 z=21 with hub

Product Description

Sprocket 20B-3 z=21, with hub

Triplex (three-strand) sprocket 20B-3 with hub, 21 teeth - designed for chain with a pitch of 1 1/4" (31.75 mm). The sprocket complies with DIN 8187 / ISO 606 and is made of C45E steel (EN 10083-1); the teeth are not hardened, which lowers the cost of the sprocket and makes it easier to machine (e.g. deep boring of the hub) throughout the entire volume of the material.

Technical data

Frequently asked questions

Does a larger number of teeth always mean a longer service life for the sprocket?

Largely yes - the more teeth are engaged, the lower the load on each individual tooth, and the chain runs over a larger wrap angle, which reduces dynamic impacts. Very small sprockets (with fewer than fifteen or so teeth) wear the fastest and are best avoided if the drive design allows.

How does rotational speed affect the selection of the minimum number of teeth of a sprocket in the system?

At higher rotational speeds, a larger minimum number of teeth on the smallest sprocket in the system is recommended to reduce chain vibration and impacts resulting from the so-called polygon effect. With very small sprockets (e.g. 9-11 teeth) and high speeds, wear and vibration levels increase significantly faster than with larger sprockets.

How do sprockets for roller chains differ from sprockets for toothed chains (silent chain)?

A sprocket for roller chain has a rounded tooth root matched to the chain roller (profile according to DIN 8187), whereas a sprocket for toothed chain (silent chain) has a flat, trapezoidal tooth profile that engages the chain plates instead of rollers. These two systems are not interchangeable.

How can you recognise a sprocket not made in accordance with the DIN 8187 profile?

Most often it is visible from the incorrect seating of the chain on the teeth - the chain "sits" on the tooth tips or too deep in the tooth roots, despite the correct pitch. In that case, it is worth placing a section of a known reference chain of this pitch on the sprocket and checking whether it engages each tooth evenly and smoothly.

Where is this product used?

This type of sprocket is used in drives of agricultural and industrial machinery, including screw and bucket conveyors, feed conveyors, packaging machines and internal transport systems.

When placing your order, please check the current stock level of this gear - the lead time depends on it and is clearly stated according to the quantity available in the given warehouse.

Product photos are for illustrative purposes only.